1. Field of the Invention
The invention relates to power tools and, in particular, to a multiple-speed gear arrangement for a planer.
2. Description of the Invention Background
Over the years, in response to consumer demand, thickness planers, i.e. planers for reducing the thickness of a piece of wood or similar materials while providing a smooth and flat finish, have been decreasing in size. Such portable planers balance the need to provide the required power to produce a smooth finish with the need to conserve space and decrease weight for portability.
One planer, such as the model Delta 22-560 planer manufactured by Delta International Machinery Corp. of Jackson, Tenn., has a 15-amp motor and a cutterhead speed of 8000 rpm. This planer is capable of handling stock of up to 12xc2xd inches wide. The feed rate of the workpiece is controlled by the speed of the infeed and outfeed rollers, which is typically, about 26 feet/minute. An electric motor drives the cutterhead by means of a belt and pulley system. The cutterhead provides input to a speed reduction gearbox, and the output speed of the gearbox drives the feed rollers by means of a chain and sprocket arrangement.
It is known that harder materials typically require lower feed rates to enable the cutterhead to produce a smooth finish. Such lower feed rates produce a greater number of cuts per inch, which ultimately results in a smoother surface as compared to faster feed rates, which cause fewer cuts per inch resulting in a rougher surface. Because the overall size of the planer is an important consideration, such planers are equipped with gearing that permits the feed rollers to operate at a single speed. Such gearing arrangements cannot be adjusted to accommodate materials of different hardnesses.
There remains, therefore, a need for a gear arrangement for a planer that overcomes the limitations, shortcomings and disadvantages of other portable planers without compromising their advantages.
The invention meets the identified needs, as well as other needs, as will be more fully understood following a review of this specification and drawings.
One embodiment of the invention includes a multiple-speed gearbox, preferably for a planer, but also for other power tools. Another embodiment of the invention comprises a planer that includes a cutterhead that is mounted on an input shaft, which is driven by an electric motor. The planer further includes an infeed and an outfeed roller, which are driven by an output shaft.
One embodiment of the gearbox includes a first input gear that is mounted on a first axis and that is rotatable by the input shaft. This embodiment further includes first and second output gears mounted on the output shaft such that they may rotate independently about the output shaft. The gearbox further includes a three-gear set that is rotatable about a second axis that is parallel to the input shaft. The three-gear set has a middle gear, a first outer gear and a second outer gear. The middle gear engages the first input gear, the first outer gear engages the first output gear, and the second outer gear engages the second output gear. The input shaft drives the first input gear through a two-gear set.
An actuator is attached to the output shaft to selectively engage the output shaft with the first output gear to provide a first output speed or with the second output gear to provide a second output speed. The output shaft drives the infeed and outfeed rollers with the first or the second speed, depending upon which outer gear is engaged with the output shaft. The actuator may also have a neutral position.
The described arrangement of the gears makes the gearbox compact, so that it may be supported between two gear plates separated by a distance of about three centimeters. The gearbox may also be used for other power tools, for example a planer/shaper or a molder.
Other features and advantages of the invention will become apparent from the detailed description of the preferred embodiments and from the claims.